A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section. The compressor section typically includes low and high pressure compressors, and the turbine section includes low and high pressure turbines.
A mid-turbine frame is sometimes provided between the high pressure turbine and the low pressure turbine to aid in supporting bearing assemblies. The low pressure turbine case requires cooling air to maintain temperatures within a desired limit. Cooling air is extracted from the compressor section and routed to a cavity within the mid-turbine frame. Cooling air from the cavity within the mid-turbine frame is then routed to cool the low pressure turbine case. In some applications, the mid-turbine frame is at a temperature such that cooling air within the cavity is heated above a temperature capable of sufficiently cooling the low pressure turbine case.
Accordingly, it is desirable to design and develop cooling features and systems for maintaining desired temperatures within the turbine case.